Synthesis and Characterization of Alkyl-Imidazolium-Based Periodic Mesoporous Organosilicas: A Versatile Host for the Immobilization of Perruthenate (RuO4−) in the Aerobic Oxidation of Alcohols

• Published in: Chemistry : a European journal 2012-10, Vol.18 (42), p.13520-13530
• Main Authors: Karimi, Babak, Elhamifar, Dawood, Yari, Omolbanin, Khorasani, Mojtaba, Vali, Hojatollah, Clark, James H., Hunt, Andrew J.
• Format: Article
• Language: English
• Subjects: Adsorption; Alcohols - chemistry; Catalysis; Chemistry; Imidazoles - chemistry; ionic liquids; Ionic Liquids - chemistry; mesoporous materials; organosilicas; Organosilicon Compounds - chemical synthesis; Organosilicon Compounds - chemistry; Oxidation; Oxidation-Reduction; perruthenate; Porosity; Ruthenium Compounds - chemistry; Silicon Dioxide - chemistry; Spectrum analysis; Studies; supported catalysts
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201200380

The preparation and characterization of a set of periodic mesoporous organosilicas (PMOs) that contain different fractions of 1,3‐bis(3‐trimethoxysilylpropyl)imidazolium chloride (BTMSPI) groups uniformly distributed in the silica mesoporous framework is described. The mesoporous structure of the materials was characterized by powder X‐ray diffraction, transmission electron microscopy, and N2 adsorption–desorption analysis. The presence of propyl imidazolium groups in the silica framework of the materials was also characterized by solid‐state NMR spectroscopy and diffuse‐reflectance Fourier‐transform infrared spectroscopy. The effect of the BTMSPI concentration in the initial solutions on the structural properties (including morphology) of the final materials was also examined. The total organic content of the PMOs was measured by elemental analysis, whereas their thermal stability was determined by thermogravimetric analysis. Among the described materials, it was found that PMO with 10 % imidazolium content is an effective host for the immobilization of perruthenate through an ion‐exchange protocol. The resulting Ru@PI‐10 was then employed as a recyclable catalyst in the highly efficient aerobic oxidation of various types of alcohols. Go green: The synthesis and characterization of a range of periodic mesoporous organosilica materials with different compositions of alkyl imidazolium ionic‐liquid moieties (PMO‐IL) is described (see scheme). As part of this study, the materials were also used for immobilization of perruthenate through an ion‐exchange protocol. The resulting Ru@PI‐10 was then employed as a recyclable catalyst.